A. John Adams to John Quincy Adams - May 18, 1781:

You go on, I presume, with your Latin exercises: and I wish to hear of your beginning Sallust who is one of the most polished and perfect of the Roman Historians, every period of whom, and I had almost said every syllable and letter is worth studying.

In company with Sallust, Cicero, Tacitus and Livy, you will learn wisdom and virtue. You will see them represented, with all the charms which language and imagination can exhibit and vice and folly painted in all their deformity and horror.
 

B. Thomas Jefferson to William Randolph - December 17, 1808

No stile of writing is so delightful as that which is all pith, which never omits a necessary word, nor uses an Unnecessary one. The finest models of this existing are Sallust and Tacitus, which on that account are worthy of constant s study.
 

C. Thomas Jefferson to David Harding - April 20, 1824

The object of the Society (T. Jefferson Debating Society) is laudable, and in a republican nation, whose citizens are to be led by reason and persuasion, and not by force, the art of reasoning becomes of first importance. In this line antiquity has left us the finest models for imitation; and he who studies and imitates them most nearly, will nearest approach the perfection of the art. Among these I should consider the speeches of Livy, Sallust, and Tacitus, as pre-eminent specimens of logic, taste, and what sententious brevity which using not a word to spare, leaves not a moment for inattention to the hearer.